Vegetable and animal fats are organic lipid materials that generally contain esters of long-chain fatty acids and glycerine. Under certain conditions these esters react with water (hydrolysis) to form an alcohol (glycerine) and fatty acids. (Hydrolysis is the splitting of a compound into components by the addition of water and an enzyme, acid or base.) The results of a hydrolysis reaction are known as “hydrolysates”. When heated in the presence of an alkali hydroxide, the above-mentioned esters yield soaps (alkali salts of the corresponding fatty acid) and glycerine; this particular hydrolysis process is called saponification. “Saponification” and “saponifying” are used herein in their normal manner to mean the hydrolysis reaction between a wax, oil or fat with an alkali metal or alkaline earth metal hydroxide to form the corresponding metallic salt soap. These fats and oils have a saponification value that is the number of milligrams of potassium hydroxide required for complete saponification of one gram of free organic acid and/or organic acid ester.
The post-saponification products may either be hydrophilic (water soluble) or hydrophobic (water insoluble). Herein, we will use the term “unsaponifiable” to mean those materials that, after the saponification reaction is completed, remain water insoluble. This is in full accordance with A.O.C.S. Official Method Ca 6b-53, which defines unsaponifiable materials as those substances frequently found as components of fats and oils, which cannot be saponified by the usual caustic treatment, but that are soluble in ordinary fats and oils. Included in, but not limited to, the group of unsaponafiable materials are higher aliphatic alcohols, sterols, pigments, mineral oils, and hydrocarbons. Unsaponifiable materials are generally non-volatile at 103° C. The weight percent of unsaponifiable material in a substance may be measured directly by measuring the weight percent of those materials defined as unsaponifiable.
Most well-known vegetable and animal lipids have low levels, less than 5 weight percent (<5%), of unsaponifiable materials. This means that most of the products of the saponification reaction are water-soluble. Commonly used vegetable oils have levels of unsaponifiable materials generally below 1 weight percent. For example, saponification of soybean oil leaves 0.7 weight percent unsaponifiable materials, saponification of olive oil leaves 1.2 weight percent unsaponifiable materials, and saponification of peanut oil leaves 0.4 weight percent unsaponifiable materials. However, some commercial oils contain higher concentrations of unsaponifiable products, up to as much as 6.0 weight percent unsaponifiable materials. Examples include: crude rice bran oil, 4.2 weight percent unsaponifiables; crude wheat germ oil, 6 weight percent unsaponifiables; and shea butter, 9-to 13 weight percent unsaponifiables. Materials with high levels of unsaponifiables, such as shea butter, are not a preferred starting material for the production of soap because of the relatively high amount of unsaponifiable materials left after the saponification reaction.
In most cases, the hydrolysis products of a saponification process are used for a single purpose—as hygienic skin-cleansing agents (i.e., soaps). In the past, the basic ingredient of soap was animal fat (also known as lard or tallow) with wood ash-based lye used in the saponification process. Ideally, a bar of soap has a suitable hardness to maximize user cycles and has a certain amount of resistance to water reabsorption when not in use, while at the same time providing sufficient lather (i.e., acting as a foaming agent) to enhance the cleaning ability of the soap. Animal lipids as the active ingredient in the soap making process will generally meet these user demands to a greater or lesser degree. Current soap production continues to rely heavily on animal fats in their production to meet consumer demand and manufacturing requirements, although more and different types of synthetic materials have found use in modern soap compositions. Various synthetic compounds and mixtures of compounds have become popular additions in soap making technology for their improvement of soap quality and user satisfaction. However, these synthetic-based soaps are generally resistant to the natural breakdown processes (i.e., biodegradability) and are thus relatively persistent in the environment.
There are basically two distinct types of soap manufacturing processes. In a first method, oils and fats are boiled in an open kettle with caustic alkali solutions, bringing about saponification gradually until all of the fats and oils are completely saponified, followed by the removal of glycerine. This process may either run in batch or in a continuous process.
In a second method, which is typically a continuous method (but may be run in batch form), fatty acids and alkali are brought together in proper portions for complete saponification in a mixing valve or other device which brings them into intimate contact. The progress of saponification depends on the temperature, time of contact and efficiency of mixing. Concentrated solutions produced by these methods are referred to as “neat” soaps, and possess a concentration of 60-65% soap, about 35% water and traces of salt and glycerine. It is from this product that consumer soaps in the form of bars, flakes, granules and powders are produced; by first drying the neat soap into pellets having a moisture content of about 12-16% followed by finishing steps, such as milling, plodding, amalgamating, and the like.
Consumer bar soaps today are manufactured from coconut oil and/or tallow or their fatty acids. Palm kernel oil is sometimes substituted for coconut oil for economic reasons, and soaps prepared with palm kernel oil are adjusted for performance characteristics similar to non-substituted tallow/coconut formulations. Palm oil is also often substituted for tallow.
A consideration in selecting materials for making soap is the proper ratio of saturated versus unsaturated, and long-versus-short-chain fatty acids that result in a soap having the desired qualities of stability, solubility, ease of lathering, hardness, cleaning ability, and the like. It has been determined that soaps prepared from fatty acid mixtures wherein a majority of the fatty acids in the mixtures have carbon chains less than twelve atoms irritate skin. Soaps prepared from saturated C16 and C18 fatty acids are typically too insoluble for consumer use. Thus, the preferred materials for soap production have fatty acid chains between twelve and eighteen carbon atoms in length.
Saponification of tallow produces a soap comprised of a mixture of fatty acids of C14:0, C16.0, C18:0, and C18:1 (myristic, palmitic, stearic and oleic acids, respectively) and saponification of coconut oil produces a soap comprised of a mixture of fatty acids of C12:0 and C14:0 (lauric acid and myristic acid, respectively) and significant amounts of C8:0 and C10:0 fatty acids. Consumer soap preparations usually contain tallow/coconut (T/C) ratio ranges from approximately 90:10 to 75:25. Since lauric acid is found only in the coconut fraction of T/C mixtures, the most dramatic change observed in increasing the percent of the coconut fraction of T/C mixtures is the increase in lauric acid. Increasing the coconut fraction in T/C fatty acid containing soaps generally improves the desirable foaming characteristics of such soaps. However, in soaps with T/C ratios of 50:50, the desirable skin mildness properties are reduced.
Typical fatty acid distribution (in weight percent) of the main soap making components is given below:
Carbon ChainLengthTallowPalmCoconutPalm Kernel10:0 (capric)0.10.015.16.412:0 (lauric)0.10.348.046.714:0 (myristic)2.81.317.516.216:0 (palmitic) 24.947.09.08.618:0 (stearic)20.44.59.08.618:1 (oleic)43.636.15.716.118:2 (linoleic)4.79.92.62.918:3 (linolenic)1.40.20.00.020:0 (arachidic)1.80.30.00.4
From the table it can be seen that the coconut and palm kernel fats (both known as lauric fats) are particularly rich in the C10-14 saturated fatty acids, particularly derivatives from lauric acid itself. Another fat that contains saturated, relatively short chain fatty acids similar to coconut oil is babassu oil. In contrast, tallow and palm oil per se are industrial sources of non-lauric fats, especially those containing C16 and C18 fatty acids.
In general the longer chain fatty acid alkali salts, particularly the less expensive C16 and C18 salts (as obtained from tallow and palm oils), provide structure in the finished soap bars and prevent or retard disintegration of the soap bar on exposure to water. The more expensive, shorter chain, lauric fat-derived, (i.e., lauric acid salts) and other soluble salts (typically as obtained from coconut and palm kernel oil) contribute to the lathering properties of the overall composition. A general problem in the formulation of bar soaps has been finding a balance between providing structure (generally obtained from the long chain component) and maintaining lathering properties (generally obtained from the more expensive short chain component) at a practical overall cost.
In addition to fatty acid salts, soap bars can contain free fatty acids. The addition of free fatty acids is known as “superfatting”. Superfatting at a 5-10% free fatty acids level is known to give a copious, creamy lather. Other superfatting agents used include citric and other acids that function by promoting the formation of free fatty acids in the fat blend.
For the manufacture of the soap cakes, common additives can be added to the base soap in conventional quantities, such as overgreasing agents (1 to 3 weight percent), stabilizers (antioxidants, complexing agents) (0.05 to 0.5 weight percent), perfume (0.5 to 3 weight percent) and possibly dyes (0.05 to 0.3 weight percent) as well as skin protection agents such as sorbitol, glycerine or the like (1 to 5 weight percent).
The pharmaceutical and cosmetic industries have been using fat extracts of vegetable origin since earliest times. A number of years ago it became apparent in these industries that particularly valuable biological properties resulted from the use of vegetable fats or extracts of vegetable fats rich in unsaponifiable materials. Certain vegetable oils, for example avocado, and, in particular, shea butter, are known to be particularly rich in unsaponifiable materials and/or to contain, these unsaponifiable materials.
A process for enriching unsaponifiables in oils, especially shea butter, for use in cosmetic and pharmaceutical compositions is described in U.S. Pat. No. 5,679,393, issued to Laur. This process concentrates the unsaponifiable fraction of fats and oils by the processes of crystallization and fractionation. This method is expensive and it does not liberate the alcohol moiety from the starting compounds (hydrolysis). Thus, the Laur process and methods for use of the products thereof never utilize hydrolysis to create alkali salts and liberate alcohols and other unsaponifiables.
Hydrolysates applied topically to animate and inanimate objects find use in numerous non-cleansing areas ranging from cosmetic preparations, pharmaceuticals, hydration formulations, insecticides, insect repellant, and the like. One of the areas of interest created by the varied uses of topically applied agents is maximizing the duration a topically applied active agent is present on the applied surface (substantivity). As a result of this intense interest, the search for ways to improve the duration of a fixed amount of topically applied cosmetics, pharmaceuticals, and bioactive agents has been of prime importance in all areas wherein topically applied cosmetics, pharmaceuticals, and bioactive agents are employed. An example of this interest may be found in the prior art relating to sunscreen compositions.
The use of sunscreen compositions is required by a large segment of society since many of those exposed to sunlight do not have the natural pigmentation which provides protection against the harmful effects of solar radiation. Because many people show erythema under even short exposures to sunlight, there is a need for sunscreen compositions that protect against erythema-causing radiation (i.e., ultraviolet radiation) so that longer exposure to sunlight with less risk of sunburn is possible.
A variety of sunscreen compositions are known in the art. One tendency in formulating sunscreen compositions has been to prepare compositions that are water-resistant to the skin. One method is to chemically modify the ultraviolet absorber to increase its interaction with the skin using quaternizing imidazoles, as described in U.S. Pat. No. 3,506,758; another method is to copolymerize ultraviolet light absorbing monomers with other monomers to form water-resistant films, as described in U.S. Pat. Nos. 3,529,055 and 3,864,473; yet another method is to form polymeric films with water-insoluble polymers, as described in U.S. Pat. No. 3,784,488.
The use of the acid form of crosslinked ethylene-maleic anhydride copolymers to retain ultraviolet light absorbers is disclosed in U.S. Pat. No. 3,821,363. The use of water insoluble acrylate polymer is disclosed in U.S. Pat. No. 4,172,122. The use of water-insoluble, alcohol-soluble, film-forming poly-amide materials is disclosed in U.S. Pat. No. 3,895,104 solely for the purpose of providing improved substantivity.
Cosmetic and other applications of the prior art have not heretofore utilized the substantivity inherent in hydrolysates of naturally derived materials containing high unsaponifiables or long chain esters (greater than 18 carbons in length) to enhance the intrinsic substantivity of topically applied agents with which they are incorporated. The purpose of employing polymers or polymeric materials in the compositions of the prior art has been directed towards improving the adherency (i.e., substantivity) of the topical material to the skin or have been employed solely as thickening agents. The improved substantivity, among other properties, achieved by employing the hydrolysates according to the present invention has not heretofore been disclosed or appreciated in the prior art.
The increased substantivity of topically applied agents provides for more effective and economical use of such materials. In particular, the present invention provides improved compositions, including emollients, skin hydrating agents, sunscreens, lipsticks, makeup, insect repellants, insecticides, pesticides, herbicides, and the like, having at least an effective amount of a hydrolysate including high levels of unsaponifiable materials, preferably of long chain alcohols.